If you have two panels that you want to run into the one battery, but they both have their own regulator (or solar controller) and you want to know if its possible, and safe to feed them both into the same battery, this is a short post to cover the answer.
There’s a few things you should be aware of, which we’ll go into below, but in general as long as you are feeding regulated power into your batteries there shouldn’t be an issue.
There’s a theory that the two regulators can fight each other as they see the floating voltage of the battery from the other controller, but we’ve never experienced this. In the same way that you can run a DCDC battery charger taking current from your alternator and a solar controller pushing charge in from a panel at the same time, you can do both regulators at the same time too.
Our original setup was a cheap eBay solar panel with a regulator inbuilt, and then we ran a second set of folding solar panels, feeding the main battery of our 80 Series Land Cruiser. This would charge that battery, and then the Redarc isolator would open and it would charge the secondary (house) battery.
These days, we have a Renogy MPPT regulator rated at 60 amps that takes our 600W of caravan solar panels on the roof of our Reconn R2 and charges the lithium batteries, but we also have an Enerdrive DC2DC that can do alternator charge when we are driving, or an unregulated solar blanket when we pull up.
We have (not so much now), used a Kings 200W solar blanket in conjunction with the Renogy MPPT with no issues, and lots of people do this.
However, make sure that the battery voltage doesn’t do anything silly when you connect them up, that your charge profile is correct and you have regulators on any feed to your batteries!
These days, there’s some very complex solar panel installations where people are running two or more Victron 100/30 MPPT regulators together, and sometimes they are even different voltage panels, which is pretty neat.
So, in short, yes, you can run multiple solar controllers into the same battery as long as you are careful! You can also in many instances run multiple panels through one regulator, which is the better option, but there’s some other things to consider before you do this, which we’ll go into in another post.